Highly Stable and Efficient FASnI₃ -Based Perovskite Solar Cells by Introducing Hydrogen Bonding

Tin-based perovskites with narrow bandgaps and high charge-carrier mobilities are promising candidates for the preparation of efficient lead-free perovskite solar cells (PSCs). However, the crystalline rate of tin-based perovskites is much faster, leading to abundant trap states and much lower open-circuit voltage (V_oc ). Here, hydrogen bonding is introduced to retard the crystalline rate of the FASnI₃ perovskite. By adding poly(vinyl alcohol) (PVA), the OH…I^- hydrogen bonding interactions between PVA and FASnI₃ have the effects of introducing nucleation sites, slowing down the crystal growth, directing the crystal orientation, reducing the trap states, and suppressing the migration of the iodide ions. In the presence of the PVA additive, the FASnI₃ -PVA PSCs attain higher power conversion efficiency of 8.9% under a reverse scan with significantly improved V_oc from 0.55 to 0.63 V, which is one of the highest V_oc values for FASnI₃ -based PSCs. More importantly, the FASnI₃ -PVA PSCs exhibit striking long-term stability, with no decay in efficiency after 400 h of operation at the maximum power point. This approach, which makes use of the OH…I^- hydrogen bonding interactions between PVA and FASnI₃ , is generally applicable for improving the efficiency and stability of the FASnI₃ -based PSCs.